B13D5

Code

Generic B — Body

Occupant classification sensor circuit malfunction

Brand: Generic

Type: B — Body

Views: UK: 11 EN: 12 RU: 13

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged or chafed wiring in the seat harness
Corroded or loose connector pins at the sensor or module
Failed occupant classification sensor mat (pressure/capacitance sensor)
Poor ground or reference voltage to the sensor
Water ingress or contamination of the sensor mat
Faulty airbag/SRS control module or internal sensor driver

Symptoms

SRS / airbag warning lamp illuminated on dash
Passenger airbag indicator shows disabled or unavailable
Passenger-side airbag may be suppressed or remain enabled incorrectly
Stored DTC B13D5 (may be accompanied by other OCS/SRS codes)
Possible inconsistent occupied/unoccupied status in scan tool data

What to check

Read all SRS/airbag codes and freeze frame / live data with a capable scanner
Visually inspect seat wiring harness, especially where it passes through the seat frame and into the floor
Inspect connectors under the seat and at the airbag/SRS module for corrosion, bent pins or push-out terminals
Check for signs of water or contamination under the seat and around the sensor mat
Verify relevant fuses and SRS power/ground circuits
Follow OEM battery disconnect and safety procedures before disconnecting airbag-related connectors

Signal parameters

Reference supply: typically ~5 V (key ON, engine OFF) at sensor power pin — verify against OEM spec
Signal output: sensor voltage or digital value should change when weight applied/removed (often 0–5 V analog or coded value)
Ground: continuity to chassis ground with low resistance
Live-data: OCS reported status should switch between 'occupied' and 'unoccupied' when gently pressing seat
Fault types: open-circuit, short-to-ground, short-to-voltage, implausible/intermittent readings

Diagnostic algorithm

Retrieve and record all SRS/OCS codes and freeze-frame data; note conditions when code set.
Confirm battery voltage is stable. Follow OEM procedure to disable the SRS system (disconnect battery and wait specified time) before touching airbag circuits.
Visually inspect seat cover, sensor mat area, and under-seat harness for contamination, moisture, damage, or foreign objects.
With connector accessible, check connector mating, pins and terminals for corrosion, bent pins or push-outs; repair or replace connector as needed.
Reconnect battery (per OEM) and use a scan tool to monitor OCS live data. With key ON (engine OFF), measure reference voltage, signal voltage, and ground at the sensor connector — compare with OEM values and observe changes when seat is loaded/unloaded.
If signal does not change or shows opens/shorts, disconnect the sensor mat and measure continuity and resistance of individual sensor circuits (if accessible) or inspect for short-to-ground/voltage.
Wiggle test the harness while monitoring live data to check for intermittent faults where wiring moves through the seat frame.
If wiring and connectors are good but sensor still faulty, replace the occupant classification sensor mat/module following OEM replacement and calibration procedures.
After repair, clear codes and perform required occupant classification system calibration/initialization per manufacturer instructions. Verify no reoccurrence during road test and with live-data checks.
If faults persist after sensor and harness repair, consider airbag/SRS control module diagnosis or replacement by a qualified technician.

Likely causes

Broken wires where harness runs through seat frame (common from seat movement)
Connector pins bent, pushed out, or contaminated at under-seat connector
Sensor mat layer delamination or internal short
Weak or missing 5 V reference or signal ground at sensor
Intermittent circuit caused by vibration/corrosion
Failed OCS electronics inside the mat

Fault status

⚠️ Status

Occupant classification sensor circuit malfunction detected. Inspect seat sensor, wiring, connectors and SRS control module. Airbag/passenger status may be affected.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours